linux-kernel - Re: [RFC 1/2] arm64: PCI: Allow use arch-specific pci sysdata

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Date:   Mon, 29 Mar 2021 16:43:13 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Boqun Feng <boqun.feng@...il.com>
Cc:     Bjorn Helgaas <helgaas@...nel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux on Hyper-V List <linux-hyperv@...r.kernel.org>,
        linux-pci <linux-pci@...r.kernel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        "K. Y. Srinivasan" <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        Wei Liu <wei.liu@...nel.org>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Rob Herring <robh@...nel.org>, Clint Sbisa <csbisa@...zon.com>,
        Ard Biesheuvel <ardb@...nel.org>,
        Sunil Muthuswamy <sunilmut@...rosoft.com>,
        Marc Zyngier <maz@...nel.org>
Subject: Re: [RFC 1/2] arm64: PCI: Allow use arch-specific pci sysdata

On Mon, Mar 29, 2021 at 4:32 PM Boqun Feng <boqun.feng@...il.com> wrote:
>
> Hi Arnd,
>
> On Sat, Mar 20, 2021 at 05:09:10PM +0100, Arnd Bergmann wrote:
> > On Sat, Mar 20, 2021 at 1:54 PM Arnd Bergmann <arnd@...db.de> wrote:
> > >      I actually still have a (not really tested) patch series to clean up
> > > the pci host bridge registration, and this should make this a lot easier
> > > to add on top.
> > >
> > > I should dig that out of my backlog and post for review.
> >
> > I've uploaded my series to
> > https://git.kernel.org/pub/scm/linux/kernel/git/arnd/playground.git
> > pci-probe-rework-20210320
> >
> > The purpose of this series is mostly to simplify what variations of
> > host probe methods exist, towards using pci_host_probe() as the
> > only method. It does provide some simplifications based on that
> > that, including a way to universally have access to the pci_host_bridge
> > pointer during the probe function.
> >
>
> Thanks for the suggestion and code. I spend some time to catch up. Yes,
> Bjorn and you are correct, the better way is having a 'domain_nr' in the
> 'pci_host_bridge' and making sure every driver fill that correctly
> before probe. I definitly will use this approach.
>
> However, I may start small: I plan to introduce 'domain_nr' and only
> fill the field at probe time for PCI_DOMAINS_GENERIC=y archs, and leave
> other archs and driver alone. (honestly, I was shocked by the number of
> pci_scan_root_bus_bridge() and pci_host_probe() that I need to adjust if
> I really want to unify the 'domain_nr' handling for every arch and
> driver ;-)). This will fulfil my requirement for Hyper-V PCI controller
> on ARM64. And later on, we can switch each arch to this approach one by
> one and keep the rest still working.
>
> Thoughts?

That sounds reasonable to me, yes. I would also suggest you look
at my hyperv patch from the branch I mentioned [1] and try to integrate
that first. I suspect this makes it easier to do the domain rework and
possibly other changes on top.

       Arnd

https://git.kernel.org/pub/scm/linux/kernel/git/arnd/playground.git/commit/?h=pci-probe-rework-20210320&id=44db8df9d729d